Auerbach's plexus
Auerbach's plexus (or myenteric plexus) provides motor innervation to both layers of the tunica muscularis, having both parasympathetic and sympathetic input, whereas Meissner's plexus has only parasympathetic fibers and provides secretomotor innervation to the mucosa nearest the lumen of the gut. It arises from cells in the nucleus ala cinerea, the parasympathetic nucleus of origin for the tenth cranial nerve (vagus), located in the medulla oblongata. The fibers are carried by both the anterior and posterior vagal nerves. The myenteric plexus is the major nerve supply to the gastrointestinal tract and controls GI tract motility.Human Anatomy and Physiology, Marieb & Hoehn, seventh edition Anatomy A part of the enteric nervous system, Auerbach's plexus (or myenteric plexus), exists between the longitudinal and circular layers of muscularis externa in the gastrointestinal tract. It is found in the muscles of the esophagus, stomach, and intestine. The ganglia have properties similar to the CNS. These properties include presence of glia, interneurons, a small extracellular space, dense synaptic neuropil, isolation from blood vessels, multiple synaptic mechanisms and multiple neurotransmitters. Auerbach's plexus originates in the medulla oblongata, a collection of cells from the ventral part of the brain stem. The tenth of the 12 cranial nerves that come out directly from the brain, carry the bundle to its location. Mazzuoli G, Schemann M (2012) Mechanosensitive Enteric Neurons in the Myenteric Plexus of the Mouse Intestine. PLoS ONE 7(7): e39887. doi:10.1371/journal.pone.0039887 Functionality The Auerbach's plexus functions as a part of the enteric nervous system (Digestive System). The enteric nervous system can and does function autonomously, but normal digestive function requires communication links between this intrinsic system and the central nervous system. The ENS contains sensory receptors, primary afferent neurons, interneurons, and motor neurons. The events that are controlled, at least in part, by the ENS are multiple and include motor activity, secretion, absorption, blood flow, and interaction with other organs such as the gallbladder or pancreas. These links take the form of parasympathetic and sympathetic fibers that connect either the central and enteric nervous systems or connect the central nervous system directly with the digestive tract. Through these cross connections, the gut can provide sensory information to the CNS, and the CNS can affect gastrointestinal function. Connection to the central nervous system also means that signals from outside of the digestive system can be relayed to the digestive system: for instance, the sight of appealing food stimulates secretion in the stomach.Fujita, S. , Nakanisi, Y. , Taniguchi, H. , Yamamoto, S. , Akasu, T. , et al. (2007). Cancer Invasion to Auerbach's Plexus is an Important Prognostic Factor in Patients with PT3-pT4 Colorectal Cancer. Diseases of the Colon and Rectum, 50(11), 1860-1866. Neurotransmitters The enteric nervous systems makes use of over 30 different neurotransmitters, most similar to those of the CNS such as acetylcholine, dopamine, and serotonin. More than 90% of the body's serotonin lies in the gut; as well as about 50% of the body's dopamine, which is currently being studied to further our understanding of its utility in the brain. The heavily studied neuropeptide known as substance P is present in significant levels and may help facilitate the production of saliva, smooth muscle contractions, and other tissue responses Receptors Since many of the same neurotransmitters are found in the ENS as the brain, it follows that myenteric neurons can express receptors for both peptide and non-peptide (amines, amino acids, purines) neurotransmitters. Generally, expression of a receptor is limited to a subset of myenteric neurones, with probably the only exception being expression of nicotinic cholinergic receptors on all myenteric neurons. One receptor that has been targeted for therapeutic reasons has been the 5-hydroxytryptamine (5-HT)4 receptor. Activating this pre-synaptic receptor enhances cholinergic neurotransmission and can stimulate gastrointestinal motility.Critical role of 5-HT1A, 5-HT3, and 5-HT7 receptor subtypes in the initiation, generation, and propagation of the murine colonic migrating motor complex Am. J. Physiol. Gastrointest. Liver Physiol. July 1, 2010 299:G144-G157 The enteric nervous system exhibits taste receptors similar to the ones in the tongue. The taste receptor T1R3 and the taste G protein gustducin are two of the most common. These receptors sense "sweetness" in tongue and sense glucose in the enteric nervous system. These receptors help regulate the secretion of insulin and other hormones that are responsible for control blood sugar levels.Margolskee, R. , Dyer, J. , Kokrashvili, Z. , Salmon, K. , Ilegems, E. , et al. (2007). T1R3 and Gustducin in Gut Sense Sugars to Regulate Expression of Na+-glucose Cotransporter 1. Proceedings of the National Academy of Sciences of the United States of America, 104(38), 15075-15080. Role in ENS Disorders Hirschsprung's disease, it is a congenital disorder of the colon in which nerve cells of the myenteric or Auerbach's plexus in its walls, also known as ganglion cells, are absent. It is a rare disorder (1:5 000), with prevalence among males being four times that of females.Tam, P. , & Garcia-Barcelo, M. (2009). Genetic Basis of Hirschsprung's Disease. Pediatric Surgery International, 25(7), 543-558. Achalasia- is a motor disorder of the esophagus characterized by decrease in ganglion cell density in Auerbach's plexus. The cause of the lesion is unknown.Cellular and Molecular Biology (Noisy-le-grand). 1995 Dec;41(8):1033-8. "Autoantibodies to Auerbach's plexus in achalasia" Role in CNS Disorders Parkinson's Disease- Because the ENS is known as the "brain of the gut" because of its similarities to the CNS, researchers have been using colonic biopsies of PD patients, to help better understand and manage Parkinson's Disease.Shprecher, D. , & Derkinderen, P. (2012). Parkinson Disease: The Enteric Nervous System Spills Its Guts. Neurology, 78(9), 683; autho. PD patients are known to experience severe constipation due to GI tract dysfunction years before the onset of motor movement complications, which Parkinson's Disease is noteworthy for.Lebouvier, T. , Neunlist, M. , Bruley des Varannes, S. , Coron, E. , Drouard, A. , et al. (2010). Colonic Biopsies to Assess the Neuropathology of Parkinson's Disease and Its Relationship with Symptoms. Plos One, 5(9), e12728. Eponym I. History of Leopold Auerbach --> Leopold Auerbach, a neuropathologist, was one of the first to further research the nervous system using histological staining methods. References External links * Slide at ucla.edu * * * Category:Autonomic ganglia Category:Digestive system Category:Enteric nervous system